1. Field of the Invention
The present invention relates generally to flip chip bonding machines and, more particularly to a chip device bonding machine for bonding chip-shaped electronic assembly parts such as ICs or the like to a flexible board and a method thereof.
2. Description of the Prior Art
IC cards in which an IC chip is housed in a plastic card are proposed. When the IC card is manufactured, an electrode of IC chip must be interconnected to a wiring pattern of the board.
FIG. 1 of the accompanying drawings shows an example of a conventional interconnection method which utilizes a wire bonding technique.
In FIG. 1, reference numeral 1 depicts a flexible board and 2 a wiring pattern formed on the flexible board 1. An IC chip 3 is secured to the flexible board 1 by an adhesive 7 and then an electrode 3a of the IC chip 3 and the wiring pattern 2 are interconnected by means of a gold wire 5.
According to the prior-art wire bonding interconnection method, the gold wire 5 occupies a predetermined space, which unavoidably increases the thickness of the product (IC card). In order to solve this problem, an interconnection method utilizing a flip chip bonding (face-down bonding) technique, which is one of the wireless bonding techniques, is proposed.
FIGS. 2A and 2B of the accompanying drawings show a conventional interconnection method utilizing the flip chip bonding technique. In FIGS. 2A and 2B, like parts corresponding to those of FIG. 1 are marked with the same references and therefore need not be described in detail. Bumps 6 are interconnected to the wiring pattern 2 at its positions corresponding to the electrodes 3 a of the IC chip 3. A thermosetting adhesive 7 is deposited on the flexible board 1 at its position corresponding to the position at which the IC chip 3 is set, as shown in FIG. 2A.
Then, the IC chip 3 is set on the flexible board 1 such that the electrodes 3 a are faced to the bumps 6. The IC chip 3 is heated at a thermosetting temperature of the adhesive 7 and applied with a pressure so that the adhesive 7 between the electrode 3 a of the IC chip 3 and the bump 6 may be removed. Thus, the IC chip 3 is secured on the flexible board 1 and the electrodes 3 a of the IC chip 3 are interconnected to the wiring pattern through the bumps 6 as shown in FIG. 2B.
In the above-mentioned flip chip bonding process, when the adhesive 7 is heated, it is frequently observed that bubbles (chemical gas or air) are produced from the adhesive 7 and remain in the adhesive 7 between the flexible board 1 and the IC chip 3. FIGS. 3A and 3B show the condition such that bubbles 8 remain in the adhesive 7 between the flexible board 1 and the IC chip 3. FIG. 3A is a longitudinal cross-sectional view and FIG. 3B is a bottom view with the flexible board 1 being omitted.
When the bubble 8 remains between the flexible board 1 and the IC chip 3, the bubble 8 is expanded and contracted in response to the change of temperature, thereby causing the interconnection portion to be cracked or peeled off. As a result, reliability of the interconnection is deteriorated.
Therefore, according to the conventional technique, in order to remove the bubbles 8, the amount of the adhesive 7 is increased or a lot of time is spent for the heating and pressing process, which uselessly consumes the adhesive 7 or deteriorates the efficiency of manufacturing.